title: Increased Peptide Contacts Govern High Affinity Binding of a Modified TCR Whilst Maintaining a Native pMHC Docking Mode.
abstract: Natural T cell receptors (TCRs) generally bind to their cognate pMHC molecules with weak affinity and fast kinetics, limiting their use as therapeutic agents. Using phage display, we have engineered a high affinity version of the A6 wild-type TCR (A6wt), specific for the human leukocyte antigen (HLA-A(∗)0201) complexed with human T cell lymphotropic virus type 111-19 peptide (A2-Tax). Mutations in just 4 residues in the CDR3β loop region of the A6wt TCR were selected that improved binding to A2-Tax by nearly 1000-fold. Biophysical measurements of this mutant TCR (A6c134) demonstrated that the enhanced binding was derived through favorable enthalpy and a slower off-rate. The structure of the free A6c134 TCR and the A6c134/A2-Tax complex revealed a native binding mode, similar to the A6wt/A2-Tax complex. However, concordant with the more favorable binding enthalpy, the A6c134 TCR made increased contacts with the Tax peptide compared with the A6wt/A2-Tax complex, demonstrating a peptide-focused mechanism for the enhanced affinity that directly involved the mutated residues in the A6c134 TCR CDR3β loop. This peptide-focused enhanced TCR binding may represent an important approach for developing antigen specific high affinity TCR reagents for use in T cell based therapies.
authors.affiliation: Cardiff University School of Medicine, Heath Park , Cardiff , UK.
authors.forename: David K
authors.initials: DK
authors.lastname: Cole
authors.forename: Malkit
authors.initials: M
authors.lastname: Sami
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Scott
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Rizkallah
authors.forename: Oleg Y
authors.initials: OY
authors.lastname: Borbulevych
authors.forename: Penio T
authors.initials: PT
authors.lastname: Todorov
authors.forename: Ruth K
authors.initials: RK
authors.lastname: Moysey
authors.forename: Bent K
authors.initials: BK
authors.lastname: Jakobsen
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Boulter
authors.forename: Brian M
authors.initials: BM
authors.lastname: Baker
authors.lastname: Yi Li
keywords: A6 TCR; T cell; T cell receptor; crystal structure; high affinity TCR; human T leukocyte virus type 1; peptide-major histocompatibility complex; surface plasmon resonance